This is a serious problem: Better educated women have healthier and better-educated children, are more likely to work productively and have more control over their lives and marriages. So how do we get girls into school?

One possible solution — one which has received particularattention in the last few years — is providing better sanitary products for use during menstruation. As the story goes, girls miss significant amount of school during menstruation, largely because of lack of modern sanitary products, and this contributes to lower attendance rates, eventual failure, or dropping out.

Part of the appeal of this explanation is that the fix is so easy. There is no need to change attitudes about female schooling, to provide funds for uniforms or textbooks, or to construct new schools closer to girls’ homes; instead, the menstruation theory suggests simply providing sanitary products could significantly affect the education gap.

At least one sanitary product manufacturer has jumped on this fix: In 2007, Procter & Gamble announced its support for the Protecting Futures Program, which provides sanitary pads and hygiene education to girls in Africa. Other organizations (the Clinton Global Initiative, for example) have pledged millions of dollars to finance better sanitary products in the developing world.

All this is done based on the claim that girls miss significant amounts of school during their periods. But what is the evidence?

Up to now, this has been largely based on anecdotes and assumptions. For example, the World Bank concludes girls may miss up to 20 percent of school because of menstruation by simply assuming that girls never attend during their period.

New evidence, from a recent study [pdf] we undertook among adolescent girls in Nepal, calls this assumption — and the resulting conclusions — into serious question.

We started by asking girls whether they missed school during their period; similar to other studies, over half reported ever missing school days due to menstruation.

Rather than leaving the analysis there, however, we quantified the amount of school missed because of periods by collecting detailed information on dates of menstruation and school attendance for the entire school year.

Although girls in our sample were indeed less likely to attend school on days they had their period, the effect is very, very tiny. On non-period days, girls were in school about 85.7 percent of the time; on days they are menstruating, they were in school 83.0 percent of the time (a difference of only 3.2 percent).

This means that girls missed only about a third of a day per year because of their period.

We also examined whether better sanitary products had any impact on attendance; we did this by randomly providing menstrual cups to half of the girls in the sample. These products made no difference in closing the (very small) attendance gap.

Based on the evidence on schooling and in our randomized study, we conclude that better sanitary products are not likely to be an effective “quick fix” for girls’ education. This does not suggest we should limit our efforts at increasing schooling for girls, but it does point to the need for quantitative data to evaluate what efforts will be the most effective.